Chemokines constitute a family of cytokines of low molecular weight directly involved in inflammatory response, in the displacements of immune cells and in the directional migration of cellular elements. The term “chemokines”, which is a contraction of the words chemotactic cytokines, highlights the typical biological function of these cell mediators.
Chemokines are divided into two subspecies which differ according to the sequences of amino acids CC and CXC containing the two cysteine residues, invariably present in the N-terminal portion of the protein. In one case, for example in the case of monocyte chemoattractant protein-1 (MCP-1), the two cysteine residues are contiguous, in the other case, for example in the case of interleukin-8 (IL-8) and certain of its closest affines (GRO-α,β,γ, ENA-78, NAP-2, GCP-2), a second amino acid is interspaced between the two cysteines.
From the functional standpoint, chemokines are distinguished from the other cytokines by the cellular specificity of their action: each of them regulates in a specific way the migration and the functionality of a single cell species. Thus, if MCP-1 influences and directs the movements of monocytes, IL-8 performs the pre-eminent role of specific neutrophil-chemoattractant factor. Confirmation thereof is provided by the presence of high concentrations of IL-8 in the inflammatory sites and in the surrounding fluids, ascertained during the course of many acute illnesses mediated by neutrophils, as well as the prevention of the severity of tissue damage and reduced infiltration of neutrophils observed after administration of anti-IL-8 antibodies in the course of experiments conducted on animal models representing neutrophil-dependent illnesses. Typical clinical situations are the damage caused by cerebral re-perfusion and the damage caused by ischaemia and re-perfusion of the myocardium.
These observations have corroborated the hypothesis that IL-8 constitutes the principal mediator of tissue damage induced by neutrophils, so much so as to cause interleukin-8 to be proposed as optimal target for therapeutic interventions aimed at resolving acute inflammatory states mediated by neutrophils (N. Mukaida et al., Inflammation Research 47 (Suppl. 3) S151, 1998). For this purpose, as an alternative to the use of anti-IL-8 antibodies, substances of low molecular weight could be of great interest and of clinical usefulness, which, by inserting themselves in the inter-cellular and intra-cellular circuits of transmission of the signal, may be able to inhibit the migration of human neutrophils stimulated by IL-8 and by its affines in a highly specific way.
Recently PCT/EP/9907740 disclosed N-acylsulphonamides of (R)-2-arylpropionic acids having inhibitory activity on the chemotaxis of neutrophils stimulated by IL-8 irrespective of the inflammatory processes linked to inhibition of cyclo-oxygenase (COX-1 and/or COX-2).
On the other hand, the inhibition of the synthesis of prostaglandins (PGs) peculiar to the (S) enantiomers of 2-arylpropionic acids and of certain of their derivatives would appear to have a negative effect on the dynamics, of the neutrophil-dependent inflammatory process stimulated by IL-8, such as to exacerbate the illness itself. In these circumstances, with the inhibition of PG synthesis, the endogenous factor, PGE2, which controls the synthesis of Tumour Necrosis Factor-alpha (TNF-α), comes to be missing. Consequently, in competition with IL-8 itself, TNF-α may contribute, together with the cytokines IL-6 and IL-1 and with the molecules of the adhesion (E-selectin, ICAM-1 and C-reactive protein) to exacerbating the degree and severity of the tissue damage in the course of acute myocardial infarction (R. Pudil et al., Clin. Chim. Acta, 280, 127, 1999).
Also the known (R)-2-(4-isobutyl-phenyl)-propionamide (PCT/EP/9907740) has proved active in the prevention and inhibition of chemotaxis of human leucocytes induced by IL-8, a property instead altogether absent in the (S) enantiomer (Table 1).
TABLE 1% inhibition ofchemotaxis of humanPMNs stimulatedCompoundby IL-8 (10 ng/mL)(R)-2-(4-isobutyl-phenyl)-propionamide*57 ± 12(S)-2-(4-isobutyl-phenyl)-propionamide*−2 ± 8 *conc. 10−8 M
In addition, the same compound and the corresponding (R)—N-methyl-2-(4-isobutyl phenyl)-propionamide, albeit less potent [25±9% inhibition at a concentration of 10−8 M] as inhibitor of leucocyte chemotaxis stimulated by IL-8 (10 ng/mL), are characterized in that they down-regulate the production of TNF-α (stimulated in murine macrophages by H2O2 and by liposaccharides), as well as in that they do not inhibit the synthesis of PGE2 in the macrophages after stimulation with lipopolysaccharides (LPSs) at 1 μg/mL. Instead, in the same experimental conditions, S-ketoprofen (taken as a typical example of (S) enantiomer of 2-aryl-propionic acids, COX inhibitors), stimulates in macrophages the amplification of TNF-α synthesis induced by LPSs with a percent variation of 300% for the synthesis and release of TNF-α; in fact, in the presence of control values of the cytokine present in the incubation medium alone of less than the detectable minimum (20 pg/mL), values of 10±5 ng/mL are found in the presence of LPSs, whereas values of 39±5 ng/mL are found in the presence of LPSs and of S-ketoprofen 10−5 M. (Ghezzi et al., J. Pharmacol. Exp. Therap., 287, 969-974, 1998). More recently, it has been shown that this sensible increase in TNF-α release is a direct consequence of the stimulation of TNF-α-mRNA by S-ketoprofen (P. Mascagni et al., Eur. Cytokine Netw., 11:185-192,2000).
Amides of 2-arylpropionic acids with amino alcohols are described in ES 500990 and in ES 2007236 for the preparation of N-(α-hydroxyethyl)-d,1-2-(4 isobutyl)propionamides.
Also known are amides of ibuprofen with L and D, L-amino acids (W. Kwapiszewski et al., Acta Pol. Pharm., 42, 545, 1985), and more generally amides of racemates and of S-enantiomers of 2-aryl-propionic acids with glycine (P. Singh et al., Indian J. Chem., sect. B, 29B, 551, 1990) and with the following amino acids: lysine, glutamic acid, and aspartic acid [A. Reiner, U.S. Pat. No. 4,341,798].
More frequently, these compounds have been evaluated as mixtures of diastereoisomers without it being possible to define the contribution of the individual diastereoisomers.
Amides of enantiomers of 2-arylpropionic acids with taurine, glutamine, ornithine, arginine, glutamic acid, aspartic acid, serine, and alanine are known as urinary metabolites of these acids in various animal species (R. I. Jeffrey et al., Xenobiotica, 4, 253, 1978, and references cited therein).
Other amides, studied as pro-drugs of 2-arylpropionic acids, have been described by S. Biniecki et al., PL 114050, H. A. Kguen et al., Arzneim-Forsh., 46, 891, 1986 and G. L. Levitt et al., Russ. J. Org. Chem., 34, 346, 1998. Such amides are credited with quite a good anti-inflammatory activity associated to reduced side effects and good tolerability at the gastro-intestinal level that are believed to compensate for the loss of potency observed in comparison with their precursors.
The loss of every residual fibrinolytic activity has been described for (±)-ibuprofen and other non-steroidal anti-inflammatory agents, such as Indomethacin, flufenamic acid and mefenamic acid after conversion into the corresponding amides with 2-aminomethyl-pyridine (G. Orzalesi et al., Progress in Fibrinolysis and Thrombolysis, 3, 483, 1978).
In a comparative study, the anti-inflammatory, analgesic and antipyretic properties, the behavioural effects and acute toxicity in the mouse were evaluated for a series of amides of ibuprofen, of ketoprofen (both as racemates), and of 3-benzoylphenylacetic acid (R. C. W. Spickett et al., Eur. J. Med. Chem. Chim. Ther., Nov. 7, 1976). The comparison associates to the simple amides (—CONH2) and their N-ethyl and N-dimethyl derivatives, the corresponding ureides and thioureides, as well as the anilides and certain heterocyclic amides, such as those with 2-aminothiazolidine, 2-aminothiazole, 2-amino-4-methyl-pyridine and 1-phenyl-2,3-dimethyl-4-amino-pyrazole. The pharmacological study has led to the selection and development of (R,S)-2-[3-benzoylphenylpropionamido]-4-methyl-pyridine, also known by the name of Pirketoprofen [A. Gallardo, G B 1436502].
Moreover the use of R-2-arylpropionic acids as drugs for the treatment of colorectal tumours and cystic fibrosis has been recently described (U.S. Pat. No. 5,955,504 and U.S. Pat. No. 5,981,592).